| There are many processing methods which use the electrical properties of foods such as microwave heating, high frequency wave heating, ohmic heating, high voltage electrostatistic field processing, high electric field pulses, and electroosmotic dewatering et al. These methods have many advantages, compared with the conventional methods. Among them, the advantages of electromagnetic processing are as follows: I) The loss of nutrient content is very low. The foods can be heated fast and uniformly with ohmic heating. The nonthermal sterilization can realize by high voltage field pulses. 2) Most molecules and granules of foods carry electrical charge, so they can be dealt with effectively by electrical field or electromagnetic field. 3) The processing automation and precise control of food quality can be achieved by using the electrical properties of foods. 4) The electromagnetic processing possesses many traits:effective, energy saving, facile, sanitary, and controlled easily. 5) Because the energy resources of coal, oil, natural gas can't regenerate and become exhausted gradually, the nuclear power will have more and more importance on food processing in the future. It would play an important role in the food processing in future to process by using the food electric properties. Compared with thermal processing, the electrical properties of foods and their applications just have attracted many interests to study in recent several decades. It is necessary to do more research about the electrical properties of foods and their applications.Based on the study of the electrical properties of foods, heating of soybean milk and thawing of frozen meat by ohmic heating were investigated. The new measure to enhance electroosmotic dewatering was used in this thesis. The main contents of the thesis are as follows:1.An experimental device is erected to measure the electric conductivity of foods. The conductivities of soybean milk, mixture of water-starch and meat are measured on this device. The main results are: 1) The conductivity of soybean milk increases linearly with temperature and solids content. The conductivity of soybean milk which contains okara is little lower than that of the soybean milk without okara. There is no effect of electric field strength on the conductivity of soybean milk. 2) The conductivity of okara suspension increases with solid content and transits abruptly at about 60℃. The conductivity of okara suspension, which treated with 400MPa for 10mm, is larger than that of okara suspension which didn't treated, which illustrates that there are some cells undestroyed by the grinder. Heating or super high-pressure handling can destroy the cell, and lead to higher conductivity. After heated, the solid content of soybean milk, which has okara, is larger than that of soybean milk, which has not okara. 3) The conductivity of starch suspension decreases at the gelatinization temperature point on the curve of conductivity and temperature. So the gelatinization temperature can be judged by the change of electrical conductivity of starch suspension. The gelatinization temperature of the starch suspensions with water content above 50% keeps almost the same. Thegelatinization temperature increases with electric field strength. These results are similar to the results that measured by other methods. 4) The electrical conductivity of meat is relative to musculature direction in electrical field. When the musculature fibre is parallel to the field, the electrical conductivity of meat is larger than that of meat when the fibre is perpendicular to the field. The conductivity of frozen meat is relative to the unfrozen water content.2.The mathematical models of circuit analogy and unsteady heat conduction about thawing meat in solution were developed. The use factor of electrical energy, electrical distribution and temperature distribution are analyzed with these models. Experimental studies are also investigated. Ohmic heating in the solution that has certain conductivity can shorten the thawing time.
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